Control of pasteurizing systems and the like



R. E. OLSON Sept. 10, 1940.

CONTROL OF PASTEURIZING SYSTEMS AND THE MIKEv y Patented sept. 1o, 1940 lUNITED STATES- CONTROL F PASTEURIZING SYSTEMS AND THEILIKE Y Raymond E. Olson, Pittsford, N. Y., Vassigner to Taylor Instrument Companies, Rochester, N. Y., a corporation of New York Application April 4, 194.0, serial No. 327,865

A 7 Claims.

This invention relates' to the control of pasteurizing systems and the like.

In the patent to Olson No. 1,977,738, granted October 23, 1934, there is disclosed a pasteurizing system in Which'the heating of the milk or other'liquid is controlled jointly by regulating the ow of steam to the heater and by regulating the pressure of the steam supplied, the regulation of pressure and owbeing effected in response to-variations in the temperatureprevailing in the heater. By this arrangement compensation is eect'ed for wide variations in the load `on the system, where the load ,/variations/ arise from sudden changes ingthe temperature vof the 'x11 liquid being treated, or from sudden changes in the rate of the now of the' liquid through the pasteurizer.' It has been found that more satisfactory regulation is effected if relatively low pressure steam is supplied to the heater, since this permits the use of a high sensitivityV regulating instrument without thew danger of having the instrument hunt However, where such W pressure steam is-sllpplied to 'a continuous pasteurizer off-the' ow diversion type, the initial diagrammatically illustrates a pasteurizlng sys-- tem in accordance with the present invention;

Fig. A2. and Fig. 3 are modifiedarrangements which 'can be substituted for the parts shown within the dot and dash line rectangle of Fig. 1. Referring to the drawing, the reference char- 4'5 acteri generallydesrgnates a combinedpasteurizingrunit 6 and regenerating unit-1. lnV the pasteurizingunit' the milk or other liquid to be pasteurized, ows through a set oi'rcoils or plates 9 .in heat exchange relation to a set of heating 5o coils 01j-- piates 9 through which there is recirculated, water maintained at slightly above the vpasteurizing temperature.- The water recircue lating lsystenrincludes a surge tank Il from which the water is` circulated by thepump vI2 througha mixing T I3, thence through the heatheating` up period of the pasteurizer .as welll ing coils 9 of the pasteurizer and thepipe Il, back to the surge tank;` i

The regenerator unit includes two sets of coils or plates I5 and Isin heat exchange-relation through one set .of which, such as I5, the raw 6 .milk from the tank I'I is pumped by the pump P to the milk coils or plates v8 of the pasteurizer. lThe other set of coils or plates I6 lof the regenerator conduct the pasteurized milk from the pasteurizer into heat exchange `relation to the raw 10 milk in the set of coils or plates I5, thereby serving to cm1 the pasteurized milk to partially heat the raw milk. The milk ilowing from the pasteuridzer passes into a suitable holding tube T where it is held for the required fifteen-second l holding klinterval in so-called short-time pasteurization and -then )passes into the flow diversion valveI8. I f.

This ilow vd version valve I8 which may be of the general construction `disclosed in the Karst i0 application, Serial No. 269,437; iled April 22, I 1939, is of the pneumatically operated type, hav- ,l ing a diaphragm motor topA I9 which actuatesthe valve stem against the action of a spring-to properly -position the valve. An electric contact 25.

thermometer 20 which has its thermosensitive element 2l positioned in'the'milkfiowing to the inlet of the diversion valve` I8, is of such construction that when the temperature at the thermosensitive element' 2| is at'the predetermined o or pasteurizing temperature, the Bourdon spring 22 of thegcontroller closes aan electricall circuit 'for Foperating a solenoid valve 232 This' valve'.` `when `operated, in turnsupplie's compressed air from ,the supply conduit 24 to the conduitf25 and u thence to the motor top I9 of the' flow diversion valve I8 for movingv the same to its` forward flow position. With 'the vvalve I8 thus opened, the pasteurized milk fromthe tank T ows through the pipe 26 totl/fiel c'oils or plates I5 'of the regen- 40 erator unit and thence to a suitable surge tank (not` shown): or to a bottling machine. However," when the milk at the inlet to the diversion lvalve I8 is below the predetermined temperature, the-Bourdonspring' 22 of the electric contact controller will. respond toopen the abovedescribed circuit o f the solenoidvalve 23. The valve 23 will be closed in this'way tocut i the supply of compressed air -from-theconduitv 25 leading to. the top of the diversion valve. The spring of this diversion valve then operates to move its valve disks so that the improperly pasteurized milk is'dlverted through the pipe 21 tol the milk supply tank -I'I. AFrom this tank the pasteurizer unit 6 is heated by r'ecirculating wa.

A surfaces of ter maintained at the predetermined pasteuring temperature. Thi's recirculating water is heated by steam flowing from the supply pipe 29 through the controlling valve 30, steam capacity chamber 3|, controlling valve 32,pipe 29a and through the mixing T vI3 into the circulating system. The pneumatically operated valve 30 is adjusted under the control of a reset pressure controller 33 and serves to vary the pressure of the steam' supplied to the inlet port of the valve 32. However, the valve 32 isadjusted under the control of'a temperature controller 34 and serves to vary the ilow of steam into the recirculating water.

' 'Ihe reset pressure controller 33 includes a bellowsy mounted on a lever 38 which is pivoted to open therelay valve 42 so that compressed air Will be admitted t the COIldlliI; Il leading t0 the Y top of the motor diaphragm valve 38. The valve I the valve 32.

at one endr at 31. The other end oi this lever A rests on a bellows 38 which communicates with the conduit 25. 'lhe interior of the capsular bel-V lows 35 communicates through the conduit 38 with the steam chamber 3|. 'I'hus variations in' the pressure of the steam in vthe steam chamber 3| causes the capsular bellows r35 to expand andcontract accordingly, while the bellows 38 resets the pressure at which the controllerrmaintains the steam pressure in' chamber 3| 'I'he valve stemll of a relay valve l2 engages the upper the bellows 35 'so that the valve is adjusted in accordance with the expansion and contraction of the bellows 35. The inlet port of the valve I2 is connected to the compressed air supply conduit 2l, while the l outlet port of the relay valve l2 communicates through the conduit l43l with the diaphragm to'p oil the valve 30.

The temperature controller Mis provided with a tube system) including a retal bellows I5, the capillary tube 46 an'd a thermosensitive bulb 4'| to project into the circulating water. The) tube system includes a thermosensitive medium which may be mercury, oral vaporizable liquid and its vapor A relay valve I8 has its valve stem .49 projecting into engagement with the upper sur# faces of the bellows I5. Thus'as thetemperature of the recirculating water increases, the medium'in the tube system expands to cause the bellcysli to expand in like manner. The expansion ofrthis bellows forces the valve 'stem of 'the relay valve 48 in a position to open this valve so that compressed air from the conduit 2|ilows through the valve, thence through the conduit Il to the top of the motor diaphragm valve 32 causing this^valve to close and reduce the amountv of steam supplied to the water.

In thevoperation of the system, there will be a period at the beginning of the pasteurizatlon when the' milk' in the pasteurizer is below the re quired'legal temperature. The thermosensitive element\2| of Athe electric contact thermometer will 'thus be subjected to a temperature lower than vthat required. Consequently, this thermomet'er will hold open thecircuit of the solenoid -valve 23. and fthereby prevent the now of comtank I1. Sincethe/supply-of air is cut 'on from the conduit 28 by the action `of ,the solenoid valve. the bellows 38 will contract and thereby cause the lever 36 to swin'r in` 'a clockwise direction. Thisl permits the'valve stemll tomove to a position 30 thus opens and increases the pressure'of the steam supplied to the steam chamber 3|. Also, since the milk being treated is below the required temperature, heat will be rapidly transferredv from the circulating water to the milk with the result that the temperature of the water will be below the required temperature. The thermosensitive element 41 o'f the temperature controller will respond and the relay valve I8 will be closed to reduce the amount oi' compressed air supplied through conduit J to the diaphragm motor of Since this valve is of the direct acting type, its spring will tend to increase the valve opening thereby permitting a. greater amount oi.' steam to ilow from the pipe 28 into the recirculating water.

However, when. the milk has been heated to the proper pasteurizing temperature, the thermo- V`sensitive element 2| which extends into the milk -expands the bellows 38'of the pressure controllerr thereby moving thev lever 38 in a counterclockwise direction.V This movement elevates the .bellows ifsed air pressure in the conduit also Y thereby elevating the valve stem II tending 'to close the relay valve l2. The closure of this valve reduces the compressed air in the conduit 83 ieading tothe top of the motor valve n. The

spring of\ this valve thus tends to close 'it and thereby reduce the pressure of .the steam supplied 'from the steam chamber 3|.

If i'or any reason the temperature of themilk Adischarged from the pasteurizer is below the legal temperature, the electric contact thermometer 28 will be opened in the manner previously described to close the solenoid valve. This, in turn.cuts oi! compressed lair to the ilow diversion valve so that its springmoves'it into the diverting position. The decreased pressure in the conduit 2l contracts' the bellows 38 to reset the controller and y again increases the pressure of the steam supplied through the steam chamber u. rh this way, during the. initial heating perlodand also during the period when-milk is being diverted because it is be1ow` the pasteurizing temperature, the controller 33-wlll supply at increased pressure to the steam chamber 3|. In this way the duration ofthcse periods will beV reduced' but when the-milk/is at' the pssteurizing temperature.

-the steam pressure will be reduced so thata high sensitivity controller can be used withrut danger of uhunnsu A modiiled i'orm of the invention comprises a .System similar to that shown in Pig. 1 except that the steam pressure control meansot Fig. 2

is substituted for the portion of 11g. I .enclosed' bn the dot and dash rectangle. In both arrangements, however, the pressure of steam supplied .tothe -recirculated water is controlled in accordalice with valve I8. In the arrangement of Flg.2 the' controller 3| operates in response tochange in the temperaturen! theheating wateratthe thermo- 73 e operation of thev iimlrv diversion sensitive bullo 41; This controller functions to adjust ,the valve 32 which governs the ilow of steam to pipe 29a and to the water circulating system. However, Vthe pressurel of the steam supplied to the water system is governed by the valve 30a under the control of the controller 33a. It will be noted that, valve 30a is of the type that remains open except when compressed air is supplied to its motor top. This controller is not of ethe automatic reset type since its bellows35 remains in any given position of manual adjustment. Thus the bellows responds to the pressure of the steam in the'chamber 3| to position the stem 4i of the valve 42 accordingly.

As long as the milk is at the legal temperature, the solenoidvalv`e 23 will supply compressed air to conduit 25 and thence to the top I9 of the .flow diversion valve to hold this valve in the forward ow position. AAt .this time compressed air is al'so supplied through conduit 25 to the inlet port of the relay valve 42. Valve 42 under the control of bellows 35 throttles the air supplied to the motor `of fvalve 30a which changes-the pressure of the'steamgsupplied to chamber 3|.

When the temperature of the milk drops below l the legal value, the solenoid valve 23 cutsloff the supply of compressed air from conduit 2 5 with the result that the `ow diversion valve moves to its divertingposition. ,With the air supply cut oil' from the conduit 25, there willbe no compressed air applied to the diaphragm motor of `Ythe steam pressure controlling valve 30a irrespective of the adjustment of the relay valve 42, under the control 'of thev bellows. Consequently the spring of' the valve 30a willcompletely open this valve to increase the pressure of the steam supplied to the chamber 3l.'

' Also the system of Fig.l can be modified Dy substituting the arrangement of Fig. 3'for the portion of Fig. 1 enclosed within the dot and dash rectangle. y

In the arrangement of Fig. 3, the controller 33h with the motor diaphragm valve 30h, serves to maintain agiven steam pressure in the chamvber-3l `at all times, while the'contiioller 34` and its motor diaphragm throttle the flow of Vsteam through pipe 29a in accordance witlf the' temperature of-the heating Water. However, in the Imodification shown in Fig. 3, a supplemental steamsupply is connected by the pipe 29h to the 'steam pipe 29a. The ow of supplemental steam 'through pipe 29h is governed by the motor diaphragm valve 55. This valve is of the type that is opened by its spring when no compressed air is applied toits diaphragm top.` v

In this'arrangement when the milk is at the legal temperature, compressedir will be supplied through` conduit 25 to position the -ow diversion f This results in the setting of the ilow` diversion of the valve 55 opens thisvalv valve I8 in its diverting position. With compressed air cut-off from the conduit 25,-the spring so -thatthe supplemental supply of steam is i troducedl through .pipe-29h into pipe 29a. This, of course, intro' ducesmore heat into the heating water i/n/a .given interval of time so that the flow diversion valve is in its diverting position for shorter intervals.

Y aai-1,175

' said steam supply pipe;

I claim: .I A l. In apparatus of the class described, a heat exchanger including a `first passage fora liquid 'to be heated Aand a second passage in heat exchange relation theretoifor a heating medium, a

circulating system including said last-mentioned passage, a steam supply pipe, means responsive to the temperature of the medium for 'varying the ow of steam from said supply pipe to said system, means normally maintaining saidsteam i supply at a predetermined pressure, means in cluding a ow diversion valve adjustable to one f position for discharging liquid from said first passage and adjustable to another position for diverting said 1iquid to now again through said 15 passage, and means responsive to a certain range of temperature of said liquid for adjusting said ow diversion valve to its diverting position and for increasing the pressure of steam issuing from 2 2. In apparatus of the class described, a heat exchanger including a rst passage for liquid to` be heated and a second passage in heat exchange relation thereto for a heating medium, a circulating system including said last-mentioned pas- 25 sagemasteam supply, means responsive to the temperature of the mediuinjor varying the ilow of steam from said supply pipe to said system, Va steam pressure controller having ari adjustable set point for normally maintaining said steam 30 supply at a predetermined pressure, means including a ilow diversion valve adjustable to one. position for discharging liquid from said first passage aifd adjustable to another position for diverting saidliquid to iiow again through said 35 second passage, and means responsive to a certain range oi temperature of said liquid for `adjusting said ilow diversion valve toits diverting position and vior automatically resetting said con- Y troller to ahigher controlling pressure. 40 3. In apparatus .of the class described, a heat exchangen including a passage for liquid to be heatedl and a second vpassage in heat exchange relation thereto for a heating medium, a circulating systemincluding said last-mentioned pas- 45 sage, means responsive to variations in the temperature oiu the medium for introducing vheat therein to maintain the temperature of the medium at a given value, means including a flow charging liquid from said rst passage and adjustable to another position for diverting said liquid to flow again through said iirst passage,

and means responsive to a certain range of temmedium in said second passage 'for varying the 65 V diversion valve adjustable to .one position for iis- 50 il'ow of steam from said ,supplyfpipe to said sys tem, av steam pressurev controllerhaving pneumatically adjustable set point mechanism for Anormally maintaining said steam supply at a prex determined pressure, means including a flow 7 0 version value adjustable to one position for-dis charging liquid from 's'aid first Apassage and adv justable to ,a secon'dposition for diverting said liquid to ow again through said n rst passage, a

source of compressed air, and me'ais responsive 75 to a certain range of temperature of said liquid `for adjustinmsaid flow diversion valve to its di- A,circulating system including said last-mentioned passage, a steam supply and a pipe connected thereto, means responsive to the temperature of the medium for varying the ilow oi steamI from said supply pipe to said system, a steam pressure controller normally maintaining said steam supply at a predetermined pressure, said controllerY having pneumatically-operated set point mechanism operable to maintain said steamat a higher pressure value, means including a flow diversion valve adjustable to one po-` sition for discharging liquid from said passage and adjustabler to a second position for divertingv said liquid to flow againthrough said rst passage, a source of compressed air, and means responsive to a certain fange \of saidliquid for adjusting said flow diversion valve to. its diverting position and for supplying compressdair to said pneumatically operated set point mechanism.

6. Inapparatus of the class described, a heatexch'anger including a iirst p age` for liquid to be heated and a second passag in heat exchange relation thereto for a-heating medium,a heat circulating system including saidJlast-mentioned passage, a steam supply and a pipe connected thereto, means responsive to the temperature of the medium for varying the flow of steam from said supply pipe to said system, a steam pressure controller normally maintaining said'steam supply at a predetermined pressure, said controller having pneumatically-operated set-point 5 mechanism for maintaining`said steam at a higher ress'ure value, means including a pneumatic y-operated ilow diversion valve adjustable to one position for discharging liquid from said passage and adjustable to a secl0 ond position for diverting said liquid to a ilow, again through said ilrst passage, a source of compressed air, and Ymeans responsive to a certain range of temperature of the .liquid inJ said ilrst passage for applying compressed air 15 to said flow 'diversion'valve to adjust'it to its diverting position andv for supplying compressed air to said pneumatically-operated set point mechanism. i

7. In apparatus of the class described, a heat 20 exchanger including -a/ e for liquid to be heated and a second passage inheat exchange relation thereto for a heating medium, a cir,

culating system including said .last-mentioned passage, means, responsive to variations in the .25

temperature of the medium forintroducingheat therein, means including 'a ilow diversion valve adjustable' to one position for discharging liquid from said first passage and adjustable to another position for diverting saidiiquid io now again I0 through said passage, and means responsive certain range of temperature of said liquid for adjstingsaid ilow Cdiversion valve/to its divertingdposition and for increasing the rate of heat transfer between said medium and liquid. .u

Eamonn E. OLSON. 

